Officials say policeman who was under investigation as part of high-profile royal insult probe died in custody after he hanged himself in his cell.

BANGKOK —

A policeman who was under investigation as part of a high profile royal insult probe has died in custody after he hanged himself in his cell, Thailand's justice minister on Sunday.

Police Major Prakrom Warunprapa had been jailed by a court on Wednesday along with two other people as part of a probe into a group of people who allegedly falsely claimed ties to the monarchy for personal benefit.

The other two people charged are Suriyan Sujaritpalawong, a well-known fortune teller, and his assistant, Jirawong Wattanathewasilp.

Prakrom hanged himself in his cell on Friday and was pronounced dead after being taken to hospital, said Justice Minister Paiboon Koomchaya.

"It would appear that the suspect hung himself. The jailed person was found dead in his cell and authorities tried to revive him," Paiboon told Reuters.

"Right now we are doing the autopsy. Whatever the result we will have to accept it because this is a high profile case of huge public interest."

Lese-majeste law

Thailand has the world's harshest lese-majeste law, which makes it a crime to defame, insult or threaten the king, queen, and heir to the throne or regent. Under Article 112 of the criminal code, anyone convicted of insulting the monarchy faces up to 15 years in jail for each offence.

The investigation comes at a time of heightened anxiety over the health of 87-year-old King Bhumibol Adulyadej, who is convalescing at a Bangkok hospital after being treated by doctors for “water on the brain.”

His frail health has added to the political uncertainty surrounding Thailand since a 2014 coup. Nervousness over the succession has formed the backdrop to a decade of political crisis in the country.

The investigation also comes at a time when the military government is cracking down on perceived royal defamation. There have been numerous prosecutions since the coup.

Critics of the law say it is often used to pursue opponents of the country's military and royalist elite.